This invention relates to a fuel injection nozzle for internal combustion engines and comprises a nozzle needle or pin supported in a casing and adapted for closing the orifices of the nozzle under the urgency of spring pressure and for opening them under fuel pressure. The movement of the nozzle is, being limited by stopping means, as well as by abutment means to limit the length of the opening path of the injection pin. The nozzle need is adjustable to reduce that length at idling speed, or at most at medium speed, and under a small load on the fuel combustion engine, the abutment means can be actuated by means of a spring-biassed piston being acted upon by a pressure medium.
A fuel injection nozzle of this type, for internal combustion engines, is described in German Offenlegungsschrift No. 2,558,766 (corresponding to U.S. Pat. No. 4,136,654) in which nozzle there is provided a piston which is arranged transversely to the axis of the valve pin and is displaceable hydraulically, against the action of a spring, while the surface of the piston skirt has a stepped shoulder serving as a stop for limiting the stroke of the valve pin. In this type of fuel injection nozzle, the cross sectional area opening in the injection nozzle should be smaller at idling speed and under a small partial load than under a greater load. At a greater load and speed, there should be available in the injection nozzle an opening of the greatest possible cross sectional area.
It is, however, a drawback of this known injection nozzle that the abutment means are adjustable only between one or the other of two determined end positions which causes an abrupt change in the amount of injected fuel and thereby influences unfavorably the running of the motor. When the nozzle pin hits upon a slanted segment of the piston skirt, the needle can be in a completely undefined position as the slanted face of the piston skirt segment will impart a moment of, for instance, transverse forces to the needle which may cause jamming of the needle in its guide. As, moreover, the needle is not guided in the vicinity of the piston and protrudes beyond a guide, in the nozzle body, provided at a considerable distance from the piston, it will be laterally deflected when hitting against the slanted portion of the skirt surface of the piston.